This invention relates generally to wrenches having a torque-limited drive and, more particularly, to a hand tool with an internal torque-overload coupling or clutch. It is well known to provide power tools with a torque-overload coupling which is disengaged when a selected maximum load torque is exceeded. The torque transmitting coupling or clutch usually comprises a driving element which transmits driving torque to a driven element through the use of balls or roller with seating grooves. The balls are either carried by or engaged by a spring-biased conical element into driving position with respect to the grooves. Excess torque urges the balls against the conical element. This condition produces high frictional forces between the balls and conical element. Continued re-engagement and disengagement of the coupling element against the spring loading, results in rapid wear of the engaging surfaces and in a change in the amount of the torque required for disengagement. Most of the prior art torque overload wrenches have no provision for adjusting the coupling to disengage under different driving torques and those that are so provided are either complex or have limited adjustability. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a torque-limited wrench which avoids all of the problems of the prior art wrenches by providing a torque-limiting clutch in which there is no axial displacement of the cone element during de-clutching.
Another object of this invention is the provision of a torque wrench in which displacement forces for de-clutching are applied directly against the clutch spring.
A further object of the present invention is the provision of a torque wrench in which displacement of the clutch element biased by the clutch spring is along a line extending transversely of the torque axis.
It is another object of the instant invention to provide a torque wrench having means for adjusting the clutch for changing the selected maximum torque value for de-clutching.
A still further object of the invention is the provision of a torque wrench in which the means for selecting the maximum torque value for de-clutching is simple and precise.
It is a further object of the invention to provide a torque wrench in which the means for adjusting the clutch is provided with a torque scale caliberated to measure the amount of maximum torque required to disengage the clutch.
It is a further object of the invention to provide a torque wrench which is particularly adapted for hand-operation.
It is a further object of the invention to provide a torque wrench which is sturdy, reliable, simple in construction, and easy to manufacture.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.